PREDICTION OF THE EFFECTIVE MOISTURE DIFFUSIVITY IN GELATINIZED FOOD SYSTEMS

Gelatinized food systems develop a porous structure during dehydration; therefore, the moisture diffusivity calculated from such experiments should be considered as an effective diffusion coefficient. In this work, the effective moisture diffusivity of gelatinized starches was determined from drying experiments using the method of slopes. A methodology is presented which permits the calculation of the effective moisture diffusivity from the diffusion coefficients of the two phases (air-solid) and the porosity of the system. The diffusion coefficient of the homogeneous solid phase (gel) was estimated from the calculated values of the effective diffusion coefficient, using non-linear regression analysis. Its value depends on the moisture content and temperature and varies in the range 1.4 X 10(-11) to 2.6 X 10(-10) m2/s for Amioca and 4.1 X 10(-11) to 3.2 x 10(-10) m2/s for Hylon 7.